on iphone go to settings --> general --> reset --> reset network settings
then go to settings --> personal hotspot --> turn it on and change WiFi password.
Did this work?
Checking in to see if you still need help with this issue, if so please reply at your convenience.
Do you have everything backed up to cloud?
Then could restore entire phone from a backup.
I do have issues sometimes where I have to turn it off/on a few times before I can connect, but after that its fine.
It's possible the signal is not very good so it's not picking up the hot spot.